Nuclear Theory·nucl-th

Thursday·October 29, 2015

10 papers—6 primary·4 cross-listed

01
[Submitted on 28 Oct 2015]
Current status of dynamical modeling of fluctuations at the QCD phase transition in heavy-ion collisions
Marlene Nahrgang🇺🇸
For a complete understanding of the QCD phase diagram it is important to connect first-principle thermodynamic calculations to experimental data from the RHIC Beam Energy Scan and the future experimental facilities FAIR, GSI, and NICA, Dubna. This can only be achieved by a realistic modeling of the dynamical evolution of critical fluctuations in heavy-ion collisions at the QCD phase transition. In this note I will summarize the current status of these dynamical models and highlight some of the important issues, which need to be addressed in the future.
Comments:
Published in the proceedings of the 9th International Workshop on Critical Point and Onset of Deconfinement (CPOD 2014) C14-11-17.2
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1510.08146 [pdf]
PoS(2015)·7 citations
02
[Submitted on 28 Oct 2015]
Fluctuations of flow harmonics in Pb+Pb collisions at $s_{N N} = 2.76$ ~TeV from the Glauber model
Maciej Rybczynski🇵🇱 · Wojciech Broniowski🇵🇱
In the framework of the Glauber model as implemented in GLISSANDO 2, we study the fluctuations of flow harmonics in Pb+Pb collisions at the LHC centre-of-mass energy of 2.76 TeV. The model with wounded nucleons and the admixture of binary collisions leads to reasonable agreement for the ellipticity and triangularity fluctuations with the experimental data from the ATLAS, ALICE, and CMS collaborations, verifying the assumption that the initial eccentricity is approximately proportional to the harmonic flow of charged particles. While the agreement, in particular at the level of event-by-event distributions of eccentricities/flow coefficients in not perfect, it leads to a fair (at the level of a few percent for all centralities except the most peripheral collisions) description of the scaled standard deviation and the F measure which involve the four-particle cumulants. We also discuss the case of quadrangular flow. Computer scripts that generate our results from the GLISSANDO 2 simulations are provided.
Comments:
12 pages, 6 figures, misprint in Eq. (4) corrected
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
1510.08242 [pdf]
Acta Phys.Polon.B(2016)·10 citations
03
[Submitted on 28 Oct 2015]
Competing $γ$ -rigid and $γ$ -stable vibrations in neutron rich Gd and Dy isotopes
R. Budaca · A. I. Budaca
An exactly separable version of the Bohr Hamiltonian which combines the $γ$ -stable and $γ$ -rigid axial vibration-rotation is used to describe the collective properties of few neutron rich transitional nuclei. The coupling between the two types of collective motion is managed through a rigidity parameter which also influences the geometry of the shape-phase space. While the $γ$ -angular part of the problem associated to axially symmetric shapes is treated within the small angles approximation and the stiff $γ$ oscillation hypothesis, the $β$ vibration is described by means of a Davidson potential. The resulting model have three free parameters not counting the scale and was successfully applied for the description of the collective spectra for few heavier isotopes of Gd and Dy. In both cases a critical nucleus was identified through a discontinuous behavior in respect to the rigidity parameter and relevant experimental observables.
Comments:
11 pages, 4 figures, 4 tables
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1510.08245 [pdf]
EPJA(2015)·11 citations
04
[Submitted on 28 Oct 2015]
Resonance Extraction from the SAID Analysis
Ron Workman · Alfred Svarc
Resonances are extracted from a number of energy-dependent and single-energy fits to scattering data. The influence of recent, precise EPECUR data is investigated. Results for the single-energy fits are derived using the L+P method of analysis and are compared to those obtained using contour integration applied to the global energy-dependent fits.
Comments:
Contribution to Hadron2015, Newport News, VA
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1510.08278 [pdf]
AIP Conf.Proc.(2016)·0 citations
05
[Submitted on 28 Oct 2015]
Properties of superheavy nuclei with Z = 124
M. S. Mehta · Harvinder Kaur · Bharat Kumar · S. K. Patra
We employ Relativistic Mean Field (RMF) model with NL3 parametrization to investigate the ground state properties of superheavy nucleus, Z = 124. The nuclei selected (from among complete isotopic series) for detailed investigation show that the nucleon density at the center is very low and therefore, these nuclei can be treated as semi-bubble nuclei. The considerable shell gap appears at neutron numbers N = 172, 184 and 198 showing the magicity corresponding to these numbers. The results are compared with the macro-microscopic Finite Range Droplet Model (FRDM) wherever possible.
Comments:
7 pages, 8 figures, Phys. Rev. C in press
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1510.08312 [pdf]
PRC(2015)·21 citations
06
[Submitted on 28 Oct 2015]
Rotating nuclei: from ground state to the extremes of spin and deformation
A. V. Afanasjev
The rotating nuclei represent one of most interesting subjects for theoretical and experimental studies. They open a new dimension of nuclear landscape, namely, spin direction. Contrary to the majority of nuclear systems, their properties sensitively depend on time-odd mean fields and currents in density functional theories. Moreover, they show a considerable interplay of collective and single-particle degrees of freedom. In this chapter, I discuss the basic features of the description of rotating nuclei in one-dimensional cranking approximation of covariant density functional theory. The successes of this approach to the description of rotating nuclei at low spin in pairing regime and at high spin in unpaired regime in wide range of deformations (from normal to hyperdeformation) are illustrated. I also discuss the recent progress and open questions in our understanding of the role of proton-neutron pairing in rotating nuclei at $N \approx Z$ , the physics of band termination and other phenomena in rotating nuclei.
Comments:
31 pages, 21 figures, chapter 8 in the book "Relativistic Density Functional for Nuclear Structure", World Scientific Publishing Company (Singapore), Editor Prof. Jie Meng, in press
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1510.08400 [pdf]
Int.Rev.Nucl.Phys.(2016)·9 citations
07
[Submitted on 27 Oct 2015] (cross-list from nucl-ex)
A Scaling Phenomenon in Shannon Information Uncertainty Difference of fragments in Heavy-ion Collisions
Chun-Wang Ma · Yi-Dan Song · Chun-Yuan Qiao · Shan-Shan Wang · Hui-Ling Wei · Yu-Gang Ma · Xi-Guang Cao
The Shannon information-entropy uncertainty (in brief as "information uncertainty") is used to analyze the fragments in the measured 140 $A$ MeV $^{40, 48}$ Ca + $^{9}$ Be and $^{58, 64}$ Ni + $^{9}$ Be reactions. A scaling phenomenon is found in the information-uncertainty difference of fragments between the reactions. The scaling phenomenon is explained in a manner of canonical ensemble theory, and is reproduced in the simulated reactions by the antisymmetric molecular dynamics (AMD) and AMD + GEMINI models. The probes based on information uncertainty, requiring no equilibrium state of reaction, can be used in the non-equilibrium system, and bridge the results of the static thermodynamics models and the evolving dynamical transport models.
Comments:
11 pages, 7 figures
Subjects:
Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1510.08095 [pdf]
J.Phys.G(2016)·17 citations
08
[Submitted on 27 Oct 2015] (cross-list from nucl-ex)
Isobaric yield ratio difference between the 140 $A$ MeV $^{58, 64}$ Ni + $^{9}$ Be reactions studied by antisymmetric molecular dynamics model
C. Y. Qiao🇨🇳 · H. L. Wei🇨🇳 · C. W. Ma🇨🇳 · Y. L. Zhang🇨🇳 · S. S. Wang🇨🇳
\item[Background] The isobaric yield ratio difference (IBD) method is found to be sensitive to the density difference of neutron-rich nucleus induced reaction around the Fermi energy. \item[Purpose] An investigation is performed to study the IBD results in the transport model. \item[Methods] The antisymmetric molecular dynamics (AMD) model plus the sequential decay model GEMINI are adopted to simulate the 140 $A$ MeV $^{58, 64}$ Ni + $^{9}$ Be reactions. A relative small coalescence radius R $_{c} =$ 2.5 fm is used for the phase space at $t =$ 500 fm/c to form the hot fragment. Two limitations on the impact parameter ( $b 1 = 0 - 2$ fm and $b 2 = 0 - 9$ fm) are used to study the effect of central collisions in IBD. \item[Results] The isobaric yield ratios (IYRs) for the large-- $A$ fragments are found to be suppressed in the symmetric reaction. The IBD results for fragments with neutron-excess $I =$ 0 and 1 are obtained. A small difference is found in the IBDs with the $b 1$ and $b 2$ limitations in the AMD simulated reactions. The IBD with $b 1$ and $b 2$ are quite similar in the AMD + GEMINI simulated reactions. \item[Conclusions] The IBDs for the $I =$ 0 and 1 chains are mainly determined by the central collisions, which reflects the nuclear density in the core region of the reaction system. The increasing part of the IBD distribution is found due to the difference between the densities in the peripheral collisions of the reactions. The sequential decay process influences the IBD results. The AMD + GEMINI simulation can better reproduce the experimental IBDs than the AMD simulation.
Comments:
6 pages, 5 figures
Subjects:
Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1510.08105 [pdf]
PRC(2015)·12 citations
09
[Submitted on 28 Oct 2015] (cross-list from hep-ph)
Radiative transitions of charmonium states in a constituent quark model
Wei-Jun Deng🇨🇳 · Li-Ye Xiao🇨🇳 · Long-Cheng Gui🇨🇳 · Xian-Hui Zhong🇨🇳
We study the electromagnetic (EM) transitions of the $n S$ , $n P$ ( $n \leq 3$ ), and $n D$ ( $n \leq 2$ ) charmonium states with a constituent quark model. We obtain a reasonable description of the EM transitions of the well-established charmonium states $J / ψ$ , $ψ (2 S)$ , $χ_{c J} (1 P)$ , $h_{c} (1 P)$ and $ψ (3770)$ . We find that the M2 transitions give notable corrections to some E1 dominant processes by interfering with the E1 transitions. Our predictions of EM decay properties for the higher charmonium states are also presented and compared with other model predictions. In particular, we discuss the EM decay properties of some $" X Y Z "$ states, such as $X (3823)$ , $X (3872)$ , $X (3915)$ , $X (3940)$ and $X (4350)$ as conventional charmonium states. Assuming $X (3872)$ as the $χ_{c 1} (2 P)$ state, our predicted ratio $Γ [X (3872) \to ψ (2 S) γ] /Γ [X (3872) \to J / ψ γ] ≃ 4.0$ is consistent with BaBar's measurement.
Comments:
17 pages, 6 figures and five tables. EM multipole transitions are defined and text is improved
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Theory (nucl-th)
arXiv:
1510.08269 [pdf]
13 citations
10
[Submitted on 28 Oct 2015] (cross-list from hep-lat)
Direct calculation of hadronic light-by-light scattering
Jeremy Green🇩🇪 · Nils Asmussen🇩🇪 · Oleksii Gryniuk🇩🇪 · Georg von Hippel🇩🇪 · Harvey B. Meyer🇩🇪 · Andreas Nyffeler🇩🇪 · Vladimir Pascalutsa🇩🇪
We report calculations of hadronic light-by-light scattering amplitudes via lattice QCD evaluation of Euclidean four-point functions of vector currents. These initial results include only the fully quark-connected contribution. Particular attention is given to the case of forward scattering, which can be related via dispersion relations to the $γ^{*} γ^{*} \to$ hadrons cross section, and thus allows lattice data to be compared with phenomenology. We also present a strategy for computing the hadronic light-by-light contribution to the muon anomalous magnetic moment.
Comments:
7 pages, 4 figures. Talk presented at the 33rd International Symposium on Lattice Field Theory (Lattice 2015), 14-18 July 2015, Kobe International Conference Center, Kobe, Japan
Subjects:
High Energy Physics — Lattice (hep-lat); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1510.08384 [pdf]
PoS(2016)·42 citations

Affiliations

first authorsco-authorsvia INSPIRE